IMPROVEMENT OF CULTURE CONDITIONS FOR L-PROLINE PRODUCTION BY A RECOMBINANT STRAIN OF SERRATIA-MARCESCENS

Serratia marcescens SP511 was previously reported to be an L-proline-p roducing strain that harbors a recombinant plasmid carrying the mutant type of the proline operon. This strain produced 65 g/L of L-proline in a medium containing 22% sucrose and urea after 5 d of incubation un der the conventional culture conditions. We searched for more suitable culture conditions for more abundant L-proline production by SP511. T o improve the supply of a nitrogen source to cells, ammonium was used instead of urea and fed to a culture under control of the pH of the me dium. The concentrations of MgSO4 and K2HPO4 were increased, and in ad dition, sucrose was continuously added to the culture at a final conce ntration of 32%. Under these conditions, the cell amount was increased twofold over that under the previous conditions and L-proline product ion reached a maximum of more than 100 g/L after 4 d in incubation.